Conventional UV systems include one or more magnetrons and a UV bulb enclosed in a lamphead. The UV bulb is mounted within a metallic microwave cavity or chamber, and the magnetrons are coupled to the interior of the microwave chamber by one or more waveguides. Upon the application of power, the magnetrons generate radio frequency (“RF”) energy into the microwave chamber through the waveguides. The RF energy excites and ignites a gas inside the UV bulb in the microwave chamber, thereby causing the gas to enter into a plasma state. As a result, the UV bulb begins to emit UV energy, which can be used for a number of applications. For example, the UV energy can be directed to a substrate for the purpose of curing materials thereon or modifying the surface thereof.
The magnetrons used in conventional UV systems are consumable items with their life determined by a number of factors, including total hours of operation, operating temperature, as well as other conditions. When a magnetron reaches the end of its life, the magnetron becomes unsuitable for use and necessary to replace. However, conventional UV systems contain certain drawbacks relative to the determination of when to replace the magnetron, and whether the replacement magnetron will be suitable for use with the UV system.
For example, operating a magnetron at higher temperatures than its rated temperature has been found to play a major role in reducing magnetron life. Conventional lampheads incorporate remote sensing devices within the lamphead for inferring the temperature of the magnetrons. Due to variations and lag caused by air flow and heat transfer in the lamphead, however, these remote sensing devices can offer inaccurate and delayed readings with respect to the operating temperature of the magnetron. As a result, conventional UV systems may fail to provide an accurate prediction of magnetron life based on the operating temperatures of the magnetron. This lack of an accurate prediction of magnetron life can cause a user to replace a magnetron earlier than is necessary, or conversely to not replace the magnetron until after it has failed. Because the downtime from replacing magnetrons can be expensive, users often opt to implement overly aggressive maintenance schedules to replace magnetrons before they fail. But aggressive replacement schedules result in added cost.
Conventional UV systems also fail to monitor for magnetron incompatibility. The intensity of the UV energy emitted from a UV system largely depends on the magnitude of the RF energy supplied by the magnetrons. To that end, conventional UV systems require high powered magnetrons having stringent specifications. Once an original manufacturer's magnetron is ready to be replaced, however, some users may replace the magnetron with one that does not meet the required specifications. Such replacements may reduce the effectiveness of the UV system or have other negative consequences.
For example, typical high volume UV systems incorporate two high powered magnetrons that supply RF energy at specific frequencies differing by 20 MHz. The 20 MHz difference is enough to prevent spectral interference between the magnetrons during operation while also optimizing the UV energy output relative to intensity and spectral output. A greater difference would adversely affect the excitement and ignition of the UV bulb, leading to longer start times and reduced emission of UV energy. Furthermore, because each waveguide that couples the magnetron to the UV bulb has geometry directly proportional to the frequency of the coupled magnetron, using a magnetron with an incompatible frequency results in reduced RF coupling with the UV bulb. Thus, using a replacement magnetron emitting an RF frequency that is too close to that of another magnetron in the same UV system may result in spectral interference and even damage. On the other hand, using a replacement magnetron emitting an RF frequency that is too distant from the RF frequency of another magnetron in that system may result in unacceptable levels or uniformity of UV output.
Other factors also affect the compatibility of a replacement magnetron with a UV system. For example, each magnetron includes a filament of a certain size and shape that is used to generate free electrons and thereby initiate the creation of the RF energy. However, improper filament size and shape for a given UV system can prevent the magnetron from starting properly or lead to magnetron damage. Furthermore, some magnetrons are simply of lesser quality and have a shorter effective life, which results in more frequent magnetron replacement. In addition, replacement magnetrons must also be compatible with the power supply of the UV system to function properly.
More recently, UV systems have been developed which use an alternative, solid state circuit to generate the necessary RF energy, which has potential advantages in manufacturing cost, durability, and other performance metrics. However, some of the concerns noted above which are applicable to magnetron RF sources are also applicable to solid state sources, such as the necessity to determine whether the solid state RF source has reached the end of it useful life, whether the solid state source is being used at an appropriate temperature and other appropriate environmental conditions and how those might effect useful life, and the need to ensure that a solid state RF source is compatible with the UV system in which it is being installed and meets the appropriate specifications for the installation environment.
For these reasons, as well as others, it is desirable to provide improved UV systems and methods for ensuring that a RF source of a UV system is suitable for use with that system.